Some people do not want to believe even in the possibility that the supernatural could exist under any circumstances
Um, no, I think the reverse is true. Almost everybody - including skeptics -
wants there to be ghosts and goblins, because that would be a lot more fun. Skeptics are usually big fans of fantasy and science fiction, and who wouldn't want to be a Jedi with a lightsaber or something?
There's hardly a widespread problem of unreasonable
disbelief in supernaturalism. Human brains just don't work like that. Everything about human cognition is biased towards finding intelligent agency "behind the scenes"; the notion that there would be any substantial number of people who would unreasonably insist in naturalism is just a non-starter.
One of my favorite quotes from the movie "The Mist" goes like this
And you're aware that the end of "The Mist" is that it turns out there never were any monsters, just a bunch of drug-induced hallucinations? And that therefore the guy shot his family for no reason at all? I wouldn't say that "The Mist" is a good example of unwarranted skepticism in the supernatural. (Those people in vampire movies who say "but there's no such thing!" even as everyone around them is
drinking blood with pointy teeth and bursting into flame in the sunlight, that's another story.)
Sorry. but basically I am asking how much evidence would it take to convince some people.
Well, I think you've answered your own question - it would take a video that didn't look glitchy or fake.
In science you're supposed to examine the evidence first without a tailored conclusion before hand and be objective.
No, in science you're supposed to explain the data at hand with the simplest explanation, the one that proposes the least untestable entities. It's called "Occam's Razor", or the principle of
parsimony. The supernatural would be substantiated when glitches, fakery, hoaxes, mental illness, and simple coincidence become less parsimonious an explanation than the existence of the supernatural.
When you come to the conclusion first and tailor all evidence to support that conclusion, that is not being objective, is it?
I don't know why you think anything is being pre-judged, here. Coming to the conclusion
first would mean determining that the video was fake before you saw it. If you watch it and
then determine the video is fake, because it looks fake, you're post-judging - arriving at a conclusion on the basis of the evidence, not before.